An apparatus for ultrasound-based temperature imaging is disclosed in the article “Three-dimensional spatial and temporal temperature imaging in gel phantoms using backscattered ultrasound” by Ajay Anand et al., IEEE Transactions on Ultrasonics, Ferreoelectrics, and Frequency Control, vol. 54, no. 1, pages 23-31 (January 2007). Ultrasound data are acquired from a gel phantom by using backscattered ultrasound, and a three-dimensional spatial and temporal ultrasound temperature distribution is determined from the acquired ultrasound data. The apparatus can measure the temperature distribution only within a temperature range below 55° C., i.e. the apparatus is not able to determine a three-dimensional spatial and temporal ultrasound temperature distribution within, for example, a therapeutic ablation temperature range of about 55 to 60° C.